Cleaning and liquid contact with solids – Processes – Work handled in bulk or groups
Reexamination Certificate
2001-10-02
2003-03-11
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Work handled in bulk or groups
C134S015000, C134S022100, C134S022180, C134S022190, C134S023000, C134S026000, C134S032000, C134S034000, C134S036000, C134S042000, C435S264000, C510S219000, C510S226000, C510S392000
Reexamination Certificate
active
06530386
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to institutional cleaning and more particularly to an automatic “mild” process for cleaning returnable bottles and other reusable containers designed to hold foods.
Many foods, more particularly dairy products and beverages, are being increasingly sold in reusable packs which, after emptying, are returned by the customer and may be reused as a pack for the same foods. Examples of foods thus packaged are milk, cocoa, cream, yoghurt, mixed milk drinks, mineral waters, fruit juices, beer, lemonade, soft drinks and other mixed beverages. The returnable containers may consist of various materials, more particularly glass or plastics, such as polycarbonate (PC), polyvinyl chloride (PVC), polyesters (for example polyethylene terephthalate, PET, or polyethylene naphthenate, PEN) and polyethylene (PE). The containers may be adapted in shape to a variety of applications. Thus, bottles are preferably used for liquids while cups or cans are preferably used for foods with a pasty, gel-like or solid consistency. In the interests of simplicity, the present specification refers solely to bottles or the cleaning of bottles in the following although other containers to be cleaned in this way and their cleaning are of course also meant to be included.
It is obvious that the used bottles returned by the consumer have to be cleaned in a hygienically satisfactory manner before they are re-used. In the institutional sector, this is normally done using fully automatic cleaning machines in which the bottles are conveyed through several cleaning zones. These cleaning machines differ in construction according to the nature of the containers and the foods used. In general, the machines comprise at least one pre-rinse zone. In at least one other following zone, the containers are treated with a cleaning solution at elevated temperature. Finally, there is at least one other zone in which the bottles are rinsed with water. The prerinse zone is also often referred to as the presoak zone and the zone in which the containers are treated with the cleaning solution as the “liquor” zone. Several separate zones may be present both for the prerinse phase, the cleaning phase and the final rinse phase. Depending on the particular application, other zones, for example a preliminary bottle emptying zone, may be provided. The contacting of the bottles with the cleaning liquids can take place differently in each zone, generally by spraying or immersion. As they pass through the machine, the bottles are normally first heated slowly in the precleaning zone, are then treated at a much higher temperature in the liquor zone and, thereafter, are cooled again in the following rinse zones. By virtue of this division into different baths and zones, detergents, water and heat are economically and effectively used.
After loosely adhering food residues and soils have been removed in the prerinse zone, the bottles are actually cleaned in the liquor zone. This zone comprises at least one station where the bottles are cleaned with a cleaning solution at high temperatures of normally about 60 to 90° C., depending on the bottle material. Particularly good cleaning effects are obtained where one to three liquor baths are combined with a following liquor spray zone. Conventional cleaning processes use as liquor a cleaning solution which contains ca. 1 to 3% of sodium hydroxide and additions of sequestering agents, surfactants and other detersive components. Hitherto, the belief was that satisfactory cleaning of the bottles in a short time could only be achieved with liquors as highly alkaline as this notwithstanding the disadvantages of using such cleaning solutions. Thus, the use of strongly alkaline liquors placed a heavy burden on wastewater treatment plants which was further increased by the presence in these strongly alkaline liquors of certain non-readily biodegradable auxiliary chemicals. In addition, the surfaces of glass bottles and various plastic bottles were attacked under the extreme conditions so that the bottles soon assumed an unattractive appearance and, in many cases, even had to be removed from the circuit at an early stage. The saponification of fat-containing residues often resulted in problems with foam. Defoamers had to be added as a countermeasure. Their critical wash-out behavior gave them the potential to contaminate the food to be packaged. Finally, the use of strongly alkaline cleaning liquors exposed the machine operator to a significant risk, of “burning”.
BRIEF SUMMARY OF THE INVENTION
Starting out from these observations, the problem addressed by the present invention was to provide an improved process for cleaning bottles which would avoid the disadvantages of conventional processes without any deterioration in the cleaning result.
It has surprisingly been found that this problem can be solved by the use of an enzyme-containing cleaning solution in the cleaning zone.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the present invention relates to a process for cleaning returnable bottles and similar containers designed to hold foods, in which the used bottles are conveyed through several zones in a bottle washing machine of which at least one zone is intended for prerinsing, at least one following zone for treatment with a cleaning solution at elevated temperature and at least one other zone for rinsing with water, at least one enzyme being added to the cleaning solution to boost its cleaning performance. Enzymes from the group of proteases, amylases, cellulases, lipases, oxidoreductases and mixtures of these enzymes are preferably used. The use of proteases, especially highly alkaline proteases, on their own or together with other enzymes is particularly preferred.
The present invention also relates to the use of a corresponding solution in the process described above.
Surprisingly, it is possible by the new process to achieve an at least equivalent result in the same short times as with conventional highly alkaline cleaning liquors, but at distinctly lower temperatures and distinctly lower pH values. In many cases, a far better cleaning result is achieved than with conventional highly alkaline cleaning liquors despite a lower concentration of active substance in the cleaning liquor. The possibility of using lower concentrations of detersive chemicals and biodegradable active substances makes the new process particularly environmentally friendly. The corrosion of the bottle surfaces is negligible and, in addition, energy is saved through the low working temperatures.
According to the invention, suitable enzymes are any enzymes which have a degrading effect on the food remains and soils to be removed. The above-mentioned enzymes from the group of proteases, arnylases, cellulases, glycosidases, lipases and oxidoreductases are particularly preferred. Through the choice of various enzymes, the cleaning process can be specifically adapted to the particular food residues to be removed. Thus, proteases are preferably used for removing protein-containing soils while amylases are preferably used for starch-containing soils and lipases for removing fatty soils. The combination of several enzymes for different substrates is recommended in cases where mixed soils are present. Accordingly, proteases are mainly used for the preferred application of the process according to the invention for cleaning bottles used for dairy products, more especially milk bottles. The use of so-called highly alkaline proteases which have an isoelectric point above pH 10 and optimal activity at a pH of about 9 to about 12 is particularly preferred. The most important representatives of this group of enzymes include certain representatives of the serine proteases known as subtilisins which are obtained from bacteria and which, as a sub-group, have acquired the common name of I-S2 in the scientific literature. This group includes, for example, the enzymes known as subtilisin 147, subtilisin 309 and subtilisin PB92 (see also R. J. Siezen et al, Protein Engineering, Vol. 4, No. 7,
Bragulla Siegfried
Glanville Brian
Kluschanzoff Harald
Laufenberg Alfred
Potthoff Andreas
Carrillo Sharidan
Henkel - Ecolab GmbH & Co. OHG
Merchant & Gould P.C.
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